Married people get used to making decisions about their family together. It becomes natural then, for them to talk about what they want to leave behind for their kids when they’ve both passed away. They often feel that they want to make this decision together too.
But here they should be careful. If the spouses wish to execute a last will and testament for their kids, for their family, or for others, they should not make a joint will. Husband and wife should still make individual wills. A joint will is void and invalid under Philippine law.
Article 818 of the Civil Code states that:
Two or more persons cannot make a will jointly, or in the same instrument, either for their reciprocal benefit or for the benefit of a third person.
A joint will made by Filipinos is prohibited for being violative of public policy. A joint will is invalid and will not be allowed to transfer property in the Philippines. This is true even if the will happens to have been made in a foreign country in which joint wills are allowed. :
Article 819. Wills, prohibited by the preceding article, executed by Filipinos in a foreign country shall not be valid in the Philippines, even though authorized by the laws of the country where they may have been executed.
The reasons have to do with the fundamental characteristics of a will:
“Joint wills, whether executed by Filipinos in the Philippines or abroad, even if such foreign country allows it, are considered void in the Philippines on grounds of public policy. A joint will is prohibited because: (1) A will is a purely personal and unilateral act and this is defeated if two or more persons make their will in the same instrument; (2) It is contrary to the revocable character of a will. If one testator revokes his will by burning the document, the other testator would have no instrument left containing her testamentary dispositions; (3) A joint will, if mutual or reciprocal, may expose a testator to undue influence and may even tempt one of the testators to kill the other.”
Philippine law views joint wills as so invalid, in fact, that it is questionable if even joint wills executed by foreigners in a foreign country can be probated in the Philippines if it affects heirs in the Philippines.
Joint wills are invalid even if many people think that making a joint will is a natural thing for close relations to do. The Supreme Court has ruled that, “It is unnecessary to emphasize that the fact that joint wills should be in common usage could not make them valid when our Civil Codes consistently invalidated them, because laws are only repealed by other subsequent laws, and no usage to the contrary may prevail against their observance”.
 Coquia, J. and Aguiling-Pangalangan, E. (2000), Conflict of Laws, Quezon City, Central Professional Books, p. 385.
 Ibid, p. 386.
 De La Cerna vs. Potot, G.R. No. L-20234, December 23, 1964.